1. Field of the Invention
The present invention relates to an apparatus for neutralizing rotary reaction force set up by the driving of casings (i.e., large-diameter steel pipes used in foundation work in construction or earth moving operations) which are rotated or oscillated to be pressed into or pulled out of the soil ground by means of an all-casing driver most suitable for a method of cast-in-place operations.
2. Prior Art
An all-casing excavation work is a typical method of cast-in-place pile operations.
Two types of apparatus are currently used to neutralize rotary reaction force for all-casing drivers In one type of such apparatus, a hole is made in the base frame of the all casing driver and an H-shaped beam is inserted through the hole into the ground so that the rotary reaction force set up by the rotation of the casing is neutralized by the supporting force of the ground. In the other type of stopper apparatus, a frame is mounted around the all-casing driver and a counterweight is placed on the frame so that the rotary reaction force can be neutralized by the mass of the counterweight. The first type of stopper apparatus is not suitable for use in those cases where machinery is installed on an asphalt or concrete foundation. Examples of the second type of stopper apparatus are described in Unexamined Published Japanese Utility Model Application Nos. 61-193141 and 61-206740 and they are characterized by neutralizing the rotary reaction force of an all casing driver with a center-drill excavator placed on a frame connected to the driver.
The apparatus described in these publications have an inclinable cylinder by means of which the end of the pedestal of the apparatus adjacent to the all-casing driver is raised to an inclined position The pedestal is not inclined when a center-drill excavator is to be placed on it. When ready-mixed concrete is to be filled into the excavated hole after excavation has been completed, the end of the pedestal adjacent to the all-casing driver is raised so as to act as a sloping guide path for a mixer wagon.
The basic construction of these prior art apparatus is shown in FIG. 1. The pedestal 11 of the stopper apparatus for rotary reaction force is connected to an all-casing driver 1 and a center-drill excavator 10 for performing excavating operation through a casing 100 is placed on the pedestal 11. The all-casing driver 1 generally consists of a base frame la held horizontally by means of jacks 1e, an annular frame 1c capable of vertical movement along the base frame 1a by means of thrust cylinders 1b, and a casing retainer 1d with clamps that is mounted on the frame 1c and which is rotatable by such means as a motor. The casing 100 chucked by the clamps on the casing retainer 1d is pressed into the ground with the retainer 1d being rotated or swung with a motor or some other means and with the thrust cylinders 1b being contracted. The soil and sand in the casing 100 are excavated out and removed by means of either a bucket 205 on the earth drill shown as the excavator 10 or a hammer grab bucket. In order to pull out the casing 100, the casing which remains chucked by the clamps on the retainer 1d is pushed up with the retainer being rotated or swung and with the thrust cylinders 1b being extended If the excavator 10 is placed on the pedestal 11, it will effectively absorb the rotational reactive movement that occurs when the casing 100 is being pressed into or pulled out of the ground. The excavator 10 will also serve as a weight when the casing 100 is being pressed into the ground.
The apparatus having the construction described above are capable of satisfactorily absorbing the reaction force that develops when the casing is pressed into the ground. However, in order to neutralize the rotary reaction force, the construction of these apparatus dictates that the counterweight should be located in an area fairly close to the excavated hole. In other words, a considerably heavy counterweight must be used but depending on the area of the site, there has been a limit on the load that can be applied. Under certain work conditions, there is no need to install the pedestal 11 that serves both as the support of an excavator and as the ramp to guide a mixer wagon.
The apparatus described above have an inclining cylinder 210 on each side of the apparatus that inclines the pedestal so that it can be used as a ramp for guiding a mixer wagon when filling the concrete into the excavated hole. In addition, the frame on which the inclining cylinders are mounted has such a construction that its position cannot be changed depending upon whether a center-drill excavator is used or not, and this inevitably causes the frame to extend considerably far beyond the width of the all-casing driver unit. In certain cases where the excavator is not placed on the pedestal but the pedestal is put against the side of one of the crawlers of the excavator and where the concrete is to be filled into the excavated hole near the border of the site, the inclining cylinders will get in the way and make it impossible to bring the all-casing driver unit to approach the boarder to one half the width of the unit. In order to get around the small site limit, it has been necessary to make some alteration in the layout of machines, for example, positioning them slantwise.
Further, excepting the conventional apparatus described above, particularly in Europe, there has been well known an apparatus in which an all-casing driver is integrally attached to a running body of a center-drill excavator. However, such an apparatus has the disadvantage that it cannot neutralize too large rotary reaction force because the distance from the center of excavation to the center of gravity of the center-drill excavator cannot be increased.